Monolithically integrated system on chip for silicon photonics

ABSTRACT

In an example, the present invention includes an integrated system on chip device. The device is configured on a single silicon substrate member. The device has a data input/output interface provided on the substrate member and configured for a predefined data rate and protocol. The device has an input/output block provided on the substrate member and coupled to the data input/output interface. The input/output block comprises a SerDes block, a CDR block, a compensation block, and an equalizer block. In an example, the SerDes block is configured to convert a first data stream of N into a second data stream of M such that each of the first data stream having a first predefined data rate at a first clock rate and each of the second data stream having a second predefined data rate at a second clock rate. The device has a driver module provided on the substrate member and coupled to the signal processing block. In an example, the device has a driver interface provided on the substrate member and coupled to the driver module and configured to be coupled to a silicon photonics device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.application Ser. No. 14/311,004, filed Jun. 20, 2014, now U.S. Pat. No.9,547,622, which claims priority to U.S. Provisional Application Nos.61/842,337 filed Jul. 2, 2013 and 61/845,325 filed Jul. 11, 2013, eachof which is commonly assigned and incorporated by reference herein forall purposes.

BACKGROUND OF THE INVENTION

The present invention relates to telecommunication techniques. Moreparticularly, the present invention provides an integrated electricaloptics multiple chip module and methods.

Over the last few decades, the use of communication networks exploded.In the early days Internet, popular applications were limited to emails,bulletin board, and mostly informational and text-based web pagesurfing, and the amount of data transferred was usually relativelysmall. Today, Internet and mobile applications demand a huge amount ofbandwidth for transferring photo, video, music, and other multimediafiles. For example, a social network like Facebook processes more than500 TB of data daily. With such high demands on data and data transfer,existing data communication systems need to be improved to address theseneeds.

Over the past, there have been many types of communication systems andmethods. Unfortunately, they have been inadequate for variousapplications. Therefore, improved communication systems and methods aredesired.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to telecommunication techniques. Morespecifically, various embodiments of the present invention provide acommunication interface that is configured to transfer data at highbandwidth over optical communication networks. In certain embodiments,the communication interface is used by various devices, such as spineswitches and leaf switches, within a spine-leaf network architecture,which allows large amount of data to be shared among servers.

In modern electrical interconnect systems, high-speed serial links havereplaced parallel data buses, and serial link speed is rapidlyincreasing due to the evolution of CMOS technology. Internet bandwidthdoubles almost every two years following Moore's Law. But Moore's Law iscoming to an end in the next decade. Standard CMOS silicon transistorswill stop scaling around 5 nm. And the internet bandwidth increasing dueto process scaling will plateau. But Internet and mobile applicationscontinuously demand a huge amount of bandwidth for transferring photo,video, music, and other multimedia files. This disclosure describestechniques and methods to improve the communication bandwidth beyondMoore's law.

Serial link performance is limited by the channel electrical bandwidthand the electronic components. In order to resolve the inter-symbolinterference (ISI) problems caused by bandwidth limitations, we need tobring all electrical components as close as possible to reduce thedistance or channel length among them. Stacking chips into so-called 3-DICs promises a one-time boost in their capabilities, but it's veryexpensive. Another way to achieve this goal in this disclosure is to usemultiple chip module technology.

In an example, an alternative method to increase the bandwidth is tomove the optical devices close to electrical device. Silicon photonicsis an important technology for moving optics closer to silicon. In thispatent application, we will disclose a high speed electrical opticsmultiple chip module device to achieve terabits per second speed, aswell as variations thereof.

In an alternative example, the present invention includes an integratedsystem on chip device. The device is configured on a single siliconsubstrate member. The device has a data input/output interface providedon the substrate member and configured for a predefined data rate andprotocol. The device has an input/output block provided on the substratemember and coupled to the data input/output interface. In an example,the input/output block comprises a Serializer/Deserializer (SerDes)block, a clock data recovery (CDR) block, a compensation block, and anequalizer block, among others. The device has a signal processing blockprovided on the substrate member and coupled to the input/output block.In an example, the signal processing block is configured to theinput/output block using a bi-direction bus in an intermediary protocol.The device has a driver module provided on the substrate member andcoupled to the signal processing block. In an example, the driver moduleis coupled to the signal processing blocking using a uni-directionalmulti-lane bus. In an example, the device has a driver interfaceprovided on the substrate member and coupled to the driver module andconfigured to be coupled to a silicon photonics device. In an example,the driver interface is configured to transmit output data in either anamplitude modulation format or a combination of phase/amplitudemodulation format or a phase modulation format. In an example, thedevice has a receiver module comprising a transimpedance amplifier (TIA)block provided on the substrate member and to be coupled to the siliconphotonics device using predefined modulation format, and configured tothe digital signal processing block to communicate information to theinput/output block for transmission through the data input/outputinterface. In an example, the device has a communication block providedon the substrate member and operably coupled to the input/output block,the signal processing block, the driver block, and the receiver block,among others. The device has a communication interface coupled to thecommunication block. The device has a control block provided on thesubstrate member and coupled to the communication block.

In an example, the signal processing block comprises a forward errorcorrection (FEC) block, a digital signal processing block, a framingblock, a protocol block, and a redundancy block, among others. Thedriver module is selected from a current drive or a voltage driver in anexample. In an example, the driver module is a differential driver orthe like. In an example, the silicon photonics device is selected froman electro absorption modulator (EAM) or electro optic modulator (EOM),or a Mach-Zehnder modulator (MZM). In an example, the amplifiedmodulation format is selected from non-return to zero (NRZ) format orpulse amplitude modulation (PAM) format. In an example, the phasemodulation format is selected from binary phase shift keying (BPSK) ornPSK. In an example, the phase/amplitude modulation is quad amplitudemodulation (QAM). In an example, the silicon photonic device isconfigured to convert the output data into an output transport data in awave division multiplexed (WDM) signal. In an example, the control blockis configured to initiate a laser bias or a modulator bias. In anexample, the control block is configured for laser bias and powercontrol of the silicon photonics device. In an example, the controlblock is configured with a thermal tuning or carrier tuning device eachof which is configured on the silicon photonics device. In an example,the SerDes block is configured to convert a first data stream of N intoa second data stream of M.

In an example, the invention provides an integrated system on chipdevice. The device has a single silicon substrate member and a datainput/output interface provided on the substrate member and configuredfor a predefined data rate and protocol. In an example, the device hasan input/output block provided on the substrate member and coupled tothe data input/output interface. The input/output block comprises aSerDes block, a CDR block, a compensation block, and an equalizer block,among others. The device has a signal processing block provided on thesubstrate member and coupled to the input/output block. In an example,the signal processing block is configured to the input/output blockusing a bi-direction bus in an intermediary protocol. In an example, thedevice has a driver module provided on the substrate member and coupledto the signal processing block. The driver module is coupled to thesignal processing blocking using a uni-directional multi-lane bus. In anexample, the device has a driver interface provided on the substratemember and coupled to the driver module and configured to be coupled toa silicon photonics device. The driver interface is configured totransmit output data in either an amplitude modulation format or acombination of phase/amplitude modulation format or a phase modulationformat in an example. The device has a receiver module comprising a TIAblock provided on the substrate member and to be coupled to the siliconphotonics device using predefined modulation format, and configured tothe signal processing block to communicate information to theinput/output block for transmission through the data input/outputinterface. In an example, the device has a communication block providedon the substrate member and operably coupled to the input/output blockand the signal processing block, the driver block, and the receiverblock, and others, although there may be variations. In an example, thedevice has a communication interface coupled to the communication blockand a control block provided on the substrate member and coupled to thecommunication block. In an example, the control block is configured toreceive and send instruction(s) in a digital format to the communicationblock and being configured to receive and send signals in an analogformat to communicate with the silicon photonics device.

In an example, the present invention provides a monolithicallyintegrated system on chip device configured for a multi-rate andselected format of data communication. In an example, the device has asingle silicon substrate member. The device has a data input/outputinterface provided on the substrate member and configured for apredefined data rate and protocol. The device has an input/output blockprovided on the substrate member and coupled to the data input/outputinterface, which has a SerDes block, a CDR block, a compensation block,and an equalizer block. In an example, the SerDes block is configured toconvert a first data stream of N into a second data stream of M. In anexample, each of the first data stream has a first predefined data rateat a first clock rate and each of the second data stream having a secondpredefined data rate at a second clock rate. As used herein the terms“first” and “second” do not necessarily imply order and shall beconstrued broadly according to ordinary meaning. In an example, thedevice has a signal processing block provided on the substrate memberand coupled to the input/output block. The signal processing block isconfigured to the input/output block using a bi-direction bus in anintermediary protocol in an example. The device has a driver moduleprovided on the substrate member and coupled to the signal processingblock. In an example, the driver module is coupled to the signalprocessing blocking using a uni-directional multi-lane bus. In anexample, the device has a driver interface provided on the substratemember and coupled to the driver module and configured to be coupled toa silicon photonics device. In an example, the driver interface isconfigured to transmit output data in either an amplitude modulationformat or a combination of phase/amplitude modulation format or a phasemodulation format. The device has a receiver module comprising a TIAblock provided on the substrate member and to be coupled to the siliconphotonics device using predefined modulation format, and is configuredto the signal processing block to communicate information to theinput/output block for transmission through the data input/outputinterface. In an example, the device has a communication block providedon the substrate member and operably coupled to the input/output block,the signal processing block, the driver block, and the receiver block,and others, although there can be variations. In an example, the devicehas a communication interface coupled to the communication block and acontrol block provided on the substrate member and coupled to thecommunication block.

In an example, the present invention provides a monolithicallyintegrated system on chip device configured for a multi-rate andselected format of data communication. In an example, the device has asingle silicon substrate member. The device has a data input/outputinterface provided on the substrate member and configured for apredefined data rate and protocol. In an example, the device has aninput/output block provided on the substrate member and coupled to thedata input/output interface. In an example, the input/output blockcomprises a SerDes block, a CDR block, a compensation block, and anequalizer block, among others. In an example, the SerDes block isconfigured to convert a first data stream of X into a second data streamof Y, where X and Y are different integers. Each of the first datastream has a first predefined data rate at a first clock rate and eachof the second data stream has a second predefined data rate at a secondclock rate in an example. In an example, the device has a signalprocessing block provided on the substrate member and coupled to theinput/output block. In an example, the signal processing block isconfigured to the input/output block using a bi-direction bus in anintermediary protocol. In an example, the device has a driver moduleprovided on the substrate member and coupled to the signal processingblock. In an example, the driver module is coupled to the signalprocessing blocking using a uni-directional multi-lane bus configuredwith N lanes, whereupon N is greater than M such that a differencebetween N and M represents a redundant lane or lanes. In an example, thedevice has a mapping block configured to associate the M lanes to aplurality of selected laser devices for a silicon photonics device. Thedevice also has a driver interface provided on the substrate member andcoupled to the driver module and configured to be coupled to the siliconphotonics device. In an example, the driver interface is configured totransmit output data in either an amplitude modulation format or acombination of phase/amplitude modulation format or a phase modulationformat. In an example, the device has a receiver module comprising a TIAblock provided on the substrate member and to be coupled to the siliconphotonics device using predefined modulation format, and configured tothe signal processing block to communicate information to theinput/output block for transmission through the data input/outputinterface. The device has a communication block provided on thesubstrate member and operably coupled to the input/output block, thesignal processing block, the driver block, and the receiver block, amongothers. The device has a communication interface coupled to thecommunication block and a control block provided on the substrate memberand coupled to the communication block.

In an example, the device has an integrated system on chip device. Thedevice has a single silicon substrate member and a data input/outputinterface provided on the substrate member and configured for apredefined data rate and protocol. In an example, the device has aninput/output block provided on the substrate member and coupled to thedata input/output interface. In an example, the input/output blockcomprises a SerDes block, a CDR block, a compensation block, and anequalizer block, among others. The device has a signal processing blockprovided on the substrate member and coupled to the input/output block.The signal processing block is configured to the input/output blockusing a bi-direction bus in an intermediary protocol. The device has adriver module provided on the substrate member and coupled to the signalprocessing block. In an example, the driver module is coupled to thesignal processing blocking using a uni-directional multi-lane bus. In anexample, the device has a driver interface provided on the substratemember and coupled to the driver module and configured to be coupled toa silicon photonics device. In an example, the driver interface isconfigured to transmit output data in either an amplitude modulationformat or a combination of phase/amplitude modulation format or a phasemodulation format. In an example, the device has a receiver modulecomprising a TIA block provided on the substrate member and to becoupled to the silicon photonics device using predefined modulationformat, and configured to the signal processing block to communicateinformation to the input/output block for transmission through the datainput/output interface. In an example, the device has a communicationblock provided on the substrate member and operably coupled to theinput/output block, the signal processing block, the driver block, andthe receiver block, and among others. The device has a communicationinterface coupled to the communication block and a control blockprovided on the substrate member and coupled to the communication block.In an example, the device has a variable bias block configured with thecontrol block. In an example, the variable bias block is configured toselectively tune each of a plurality of laser devices provided on thesilicon photonics device to adjust for at least a wavelength ofoperation, a fabrication tolerance, and an extinction ratio.

In an example, the present invention provides an integrated system onchip device having a self test using a loop back technique. In anexample, the device has a self-test block provided on the substrate, theself test block being configured to receive a loop back signal from atleast one of the signal processing block, the driver module, or thesilicon photonics device. In an example, the self test block comprises avariable output power switch configured to provide a stress receivertest from the loop back signal.

In an example, the invention provides an integrated system on chipdevice having a redundant laser or lasers configured for each channel.In an example, the device has a plurality of laser devices configured onthe silicon photonics device. At least a pair of laser devices isassociated with a channel and coupled to a switch to select one of thepair of laser devices to be coupled to an optical multiplexer to providefor a redundant laser device.

In an example, the present invention provides an integrated system onchip device having a built-in self test technique. In an example, thedevice has a self test block configured on the silicon photonics deviceand to be operable during a test operation. In an example, the self testblock comprises a broad band source configured to emit electromagneticradiation from 1200 nm to 1400 nm or 1500 to 1600 nm to a multiplexerdevice. In an example, the broad band source can be an LED or othersuitable device. The device also includes a self test output configuredto a spectrum analyzer device external to the silicon photonics device.In an alternative example, the present includes a method of using amonolithically integrated system-on-chip device configured for amulti-rate and selected format of data communication. The methodincludes using the device that includes any of the features describedherein, and initiating a signal from the control block to initiate alaser bias or a modulator bias and tuning, using the control block, thesilicon photonics device.

The present invention achieves these benefits and others in the contextof known memory technology. However, a further understanding of thenature and advantages of the present invention may be realized byreference to the latter portions of the specification and attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following diagrams are merely examples, which should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize many other variations, modifications, and alternatives.It is also understood that the examples and embodiments described hereinare for illustrative purposes only and that various modifications orchanges in light thereof will be suggested to persons skilled in the artand are to be included within the spirit and purview of this process andscope of the appended claims.

FIG. 1 is a simplified diagram of a single hybrid die (Both electricaland optics devices are fabricated on a single hybrid die) according toan embodiment of the present invention.

FIG. 2 is a simplified diagram of a multi-chip module according to anembodiment of the present invention.

FIG. 2A is a simplified diagram of an exemplary hybrid silicon photonicsdevice.

FIG. 3 is a simplified diagram of an electrical silicon die blockaccording to an embodiment of the present invention.

FIG. 4 is a simplified diagram of high speed serial link block accordingto an embodiment of the present invention.

FIG. 5 is a simplified diagram of a digital processing/signalpre-distortion block according to an embodiment of the presentinvention.

FIGS. 6A and 6B are a simplified diagram of an electrical laser driverand TIA block diagram according to an embodiment of the presentinvention.

FIG. 7 is a simplified diagram of a silicon photonic block diagramaccording to an embodiment of the present invention.

FIG. 8 is a simplified block diagram of a multi-chip module according toan alternative embodiment of the present invention.

FIG. 9 is a simplified block diagram of data flow according to anembodiment of the present invention.

FIG. 10 is a simplified diagram illustrating a redundant laserconfiguration at a drive stage according to an embodiment of the presentinvention.

FIG. 11 is a simplified diagram illustrating a built-in self test usingan optical loop back according to an embodiment of the presentinvention.

FIG. 12 is a simplified diagram illustrating a built-in self testconfigured for optical testing according to an embodiment of the presentinvention.

FIG. 13 is a simplified diagram illustrating a variable bias for opticalelements configured within a silicon photonic device according to anembodiment of the present invention.

FIG. 14 is a simplified diagram illustrating wavelength tuningconfigured to silicon photonic device according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

This present invention relates to telecommunication techniques. Morespecifically, various embodiments of the present invention provide acommunication interface that is configured to transfer data at highbandwidth over optical communication networks. In certain embodiments,the communication interface is used by various devices, such as spineswitches and leaf switches, within a spine-leaf network architecture,which allows large amount of data to be shared among servers.

In the last decades, with advent of cloud computing and data center, theneeds for network servers have evolved. For example, the three-levelconfiguration that have been used for a long time is no longer adequateor suitable, as distributed applications require flatter networkarchitectures, where server virtualization that allows servers tooperate in parallel. For example, multiple servers can be used togetherto perform a requested task. For multiple servers to work in parallel,it is often imperative for them to be share large amount of informationamong themselves quickly, as opposed to having data going back forththrough multiple layers of network architecture (e.g., network switches,etc.).

Leaf-spine type of network architecture is provided to better allowservers to work in parallel and move data quickly among servers,offering high bandwidth and low latencies. Typically, a leaf-spinenetwork architecture uses a top-of-rack switch that can directly accessinto server nodes and links back to a set of non-blocking spine switchesthat have enough bandwidth to allow for clusters of servers to be linkedto one another and share large amount of data.

In a typical leaf-spine network today, gigabits of data are shared amongservers. In certain network architectures, network servers on the samelevel have certain peer links for data sharing. Unfortunately, thebandwidth for this type of set up is often inadequate. It is to beappreciated that embodiments of the present invention utilizes PAM(e.g., PAM8, PAM12, PAM16, etc.) in leaf-spine architecture that allowslarge amount (up terabytes of data at the spine level) of data to betransferred via optical network.

The following description is presented to enable one of ordinary skillin the art to make and use the invention and to incorporate it in thecontext of particular applications. Various modifications, as well as avariety of uses in different applications will be readily apparent tothose skilled in the art, and the general principles defined herein maybe applied to a wide range of embodiments. Thus, the present inventionis not intended to be limited to the embodiments presented, but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

In the following detailed description, numerous specific details are setforth in order to provide a more thorough understanding of the presentinvention. However, it will be apparent to one skilled in the art thatthe present invention may be practiced without necessarily being limitedto these specific details. In other instances, well-known structures anddevices are shown in block diagram form, rather than in detail, in orderto avoid obscuring the present invention.

The reader's attention is directed to all papers and documents which arefiled concurrently with this specification and which are open to publicinspection with this specification, and the contents of all such papersand documents are incorporated herein by reference. All the featuresdisclosed in this specification, (including any accompanying claims,abstract, and drawings) may be replaced by alternative features servingthe same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

Furthermore, any element in a claim that does not explicitly state“means for” performing a specified function, or “step for” performing aspecific function, is not to be interpreted as a “means” or “step”clause as specified in 35 U.S.C. Section 112, Paragraph 6. Inparticular, the use of “step of”or “act of”in the Claims herein is notintended to invoke the provisions of 35 U.S.C. 112, Paragraph 6.

Please note, if used, the labels left, right, front, back, top, bottom,forward, reverse, clockwise and counter clockwise have been used forconvenience purposes only and are not intended to imply any particularfixed direction. Instead, they are used to reflect relative locationsand/or directions between various portions of an object.

FIG. 1 is a simplified diagram of a single hybrid die (Both electricaland optics devices are fabricated on a single hybrid die) according toan embodiment of the present invention. In an example, the presentdevice comprises a single hybrid communication module made of siliconmaterial. The module comprises a substrate member having a surfaceregion, an electrical silicon chip overlying a first portion of thesurface region, an silicon photonics device overlying a second portionof the surface region, a communication bus coupled between theelectrical silicon chip and the silicon photonics device, an opticalinterface coupled to the silicon photonics device, and an electricalinterface coupled to the electrical silicon die.

FIG. 2 is a simplified diagram of a multi-chip module according to anembodiment of the present invention. In an example, the present devicecomprises a single hybrid communication module. The module comprises asubstrate member having a surface region, which can be a printed circuitboard or other member. The module comprises an electrical silicon chipoverlying a first portion of the surface region, a silicon photonicsdevice overlying a second portion of the surface region, a communicationbus coupled between the electrical silicon chip and the siliconphotonics device, an optical interface coupled to the silicon photonicsdevice, and an electrical interface coupled to the electrical silicondie.

As shown in FIG. 1, the single hybrid die includes a hybrid siliconphotonics device having an electrical circuit for processing and controland a silicon photonics module. In an example, the hybrid siliconphotonics device is described in U.S. Pat. No. 8,380,033, in the name ofFang, et al. issued Feb. 19, 2013, hereby incorporated by reference.FIG. 2A shows a simplified block diagram of an exemplary hybrid siliconphotonics device.

In this example, electro-optic device 200 includes a siliconsemiconductor slab including silicon top layer 201, vertical confinementlayer 202 and silicon substrate 203. Alternatively, substrate layer 203may be a diamond substrate, a glass substrate, or any functionalequivalent. Vertical confinement layer 202 may be formed of anydielectric material suitable for confining an optical mode (e.g., layer201 may be a silicon dioxide layer, a silicon nitride layer, or anyfunctionally equivalent insulating layer with a refractive index lowerthan silicon top layer 201).

Device 200 further includes a III-V semiconductor slab including p-typelayer 208, active layer 209 and n-type layer 210 (thereby forming aP-I-N diode). The term “p-type layer,” as used herein, describes a layercomprising a material that has more positive carriers (i.e., holes) thannegative carriers (i.e., electrons). The term “n-type layer,” as usedherein, describes a layer comprising a material that has more negativecarriers than positive carriers.

Alternatively, layer 208 may be an n-type layer, and layer 210 may be ap-type layer. Or, layers 208 and 210 may be n-type layers, while activeregion 209 may include a tunnel junction to convert n-type majoritycarriers to p-type majority carriers. This avoids the associated opticaland microwave loss of p-type materials due to the use of p-dopants.

III-V semiconductor materials have elements that are found in group IIIand group V of the periodic table (e.g., Indium Gallium ArsenidePhosphide, Gallium Indium Arsenide Nitride). The carrier dispersioneffects of III-V based materials may be significantly higher than insilicon based materials for bandgaps closer to the wavelength of thelight being transmitted or modulated, as electron speed in III-Vsemiconductors is much faster than that in silicon. In addition, III-Vmaterials have a direct bandgap which is required for the most efficientcreation of light from electrical pumping. Thus, III-V semiconductormaterials enable photonic operations with an increased efficiency oversilicon for both generating light and modulating the refractive index oflight.

Active layer 209 is of a III-V semiconductor with high electro-opticefficiency, i.e., the absorption coefficient (i.e., the imaginaryportion of the complex refractive index) and the refractive index (i.e.,the real portion of the complex refractive index) of active layer 209 iseasily affected by either the Franz Kheldysh effect if active layer 209comprises bulk material (e.g., intrinsic Indium Gallium ArsenidePhosphide or Indium Aluminum Gallium Arsenide or the Quantum ConfinedStark Effect if active layer 209 comprises multiple quantum wells.

Optical waveguide 250 is formed by ridge 260 (which is “bolded” or“thicker” in the figure for illustrative purposes only), including ridgesides 261 and 262. It is clear that in this embodiment, waveguide 250 isformed by features in the III-V region of device 200 as opposed to beingformed by features in the silicon region of the device, whereinwaveguide is formed by voids included in silicon top region. Thus, thesilicon and III-V regions of device 200 have a greater contact area thandevices in the prior art (where layer 210 was continuously coupled tolayer 201).

Overclad regions 207 may be formed on the device to improve mechanicalstability, and may be of any material used to form vertical confinementlayer 202 or any material with a lower refractive index than layer 208.Overclad regions 207 further provide vertical optical confinement andpassivation as described below. The areas adjacent to ridge sides 261and 262 provide optical confinement if left as voids (i.e., areascomprising air), but that forming overclad regions 207 provides formechanical stability in addition to optical confinement.

Thus, optical mode 213 is vertically confined by vertical confinementlayer 202, ridge 260 and overclad regions 207 while being laterallyconfined by ridge sides 261 and 262. Said ridge sides also confineinjection current from electrode 206 towards the portion of active layer209 that overlaps optical mode 213. The need for the etched regions andimplanted regions is eliminated in the example shown above.

It is understood that the optical device of FIG. 2A may be used toamplify, modulate or detect light transmitted through the opticalwaveguide of the device by applying an electrical difference tocomplimentary electrodes 206 and 212 to either forward bias (i.e., foramplification) or reverse bias (i.e., for modulation or detection) thestructure. The complex refractive index (i.e., at least one of the realand the imaginary refractive index) of at least the portion of activelayer 209 included in optical mode 213 changes based on an electricaldifference (e.g., electrical voltage, electrical field) applied toelectrodes 206 and 212. These changes to the refractive index (orindexes) are proportional to the strength of the electrical differenceapplied to electrodes 206 and 212.

In this example, electrodes 212 are coupled to n-type layer 210. Thus,it is to be understood that there is no electrical conduction throughsilicon top layer 201. As opposed to variations where electricalconduction does occur through the silicon top layer of a device,resistance is high as it determined by thin layer 210; however, thereare less processing steps needed to create device 200 and no conductivebond is required to couple the silicon region with the III-V region(i.e., no conductive bond is required to couple layers 210 and 201).

Other examples of silicon photonic devices are manufactured by IntelCorporation of Santa Clara, Calif., Skorpis Technology, Inc. 5600 EubankBlvd. NE Suite 200, Albuquerque, N. Mex. 87111, Luxtera, Inc. of 2320Camino Vida Roble, Carlsbad, Calif. 92011, Mellanox Technologies, Inc.350 Oakmead Parkway, Suite 100 Sunnyvale, Calif. 94085, and amLightwire, Inc. Headquartered in Allentown, Pa. (now Cisco Systems,Inc., Corporate Headquarters, 170 West Tasman Dr., San Jose, Calif.95134) among others.

FIG. 3 is a simplified diagram of an electrical silicon die blockaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. In an embodiment, theelectrical silicon die block is an electrical signal processing blockthat connects a low speed electrical interface to a high speed opticalinterface. There are several elements to this block diagram. As shown,the electrical silicon die block includes a high speed serial link 310,a digital signal processing/pre-distortion unit 320, and a lasermodulator driver and TIA unit 330. The high speed serial link 310includes an input/output block having an RX (receiving) functional unitand a TX (transmitting) function unit coupled to a phase lock loopcircuit. For example, the TX function unit drives the loopback signalsthat are processed by the RX functional unit. Using the high speedserial link 310, the data first is able to be converted from the manyparallel streams of lower speed data into a high speed serial stream(there may be more than one such high speed stream depending on thetotal data rate). The digital signal processing/pre-distortion unit 320is configured to process or convert digital electrical signal back andforth to optical signal and conduct all signal modulation, errorencoding/decoding, and signal distortion compensation. The high speedstreams converted by the high speed serial link 310 are then encoded anddigitally compensated to account for distortions in the transmit andreceive paths. The final interface to the optical components is achievedvia the modulator driver (transmit path) and the transimpedanceamplifier (receive path). The laser modulator driver and TIA unit 330 isconfigured to control the optical device (such as the optics siliconphotonics die on the part of the multi-chip module in FIG. 2). In aspecific embodiment, the electrical silicon die block is a single hybriddie as part of the multi-chip module shown in FIG. 2.

FIG. 4 is a simplified diagram of high speed serial link block accordingto an embodiment of the present invention. This diagram is merely anexample, which should not unduly limit the scope of the claims. One ofordinary skill in the art would recognize many variations, alternatives,and modifications. As shown, the high speed serial link block providesdetails of the signal interface between the high speed optical and thelower speed electrical sides. In an embodiment, the high speed seriallink block comprises multiple Bits Flash Samplers 410 and an All digitalSerDes core unit 420 powered under a low Vdd power supply. The samplers410 are part of RX functional unit of the input/output block 310. Theall digital SerDes core unit 420 comprises an all digital phase lockloop (PLL) block 422, a fast lock CDR block 424, and Digital offsetcalibrations and logics block 426, also belonging to the RX functionalunit (310 of FIG. 3). In another embodiment, the high speed serial linkblock is an electrical input/output block provided on either a singlechip or a silicon die of package substrate member and coupled to thedata input/output interface. Some of the essential components of theelectrical input/output block are CDR (clock and data recoverycircuits), PLL (phase lock loops), and SerDes (Serializers andDeserializers). In an example, the input/output block comprises a SerDesblock, a CDR block, a compensation block, and an equalizer block, amongothers. The output of equalizer includes receiver input. These circuitsin combination convert multiple streams of input data (electrical side)to fewer streams of output data (optical side). These circuits also needto be calibrated and controlled to operate correctly.

FIG. 5 is a simplified diagram of a digital processing/signalpre-distortion block according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. As shown,the digital processing/signal pre-distortion block comprises at least anError Encoding/Decoding block 510, an Optical Distortion/ElectricalCompensation (EDC) block 520, and a Modulation Conversion block 530. Inan example, it shows the details of a possible implementation of theelectronic processing blocks in the transmit and receive paths. In analternative embodiment, some of those blocks may be configureddifferently in the transmit versus the receive path. One of theessential blocks is the Error Encoding/Decoding block 510 which performsdata error control coding. As additional data bits are added to blocksof signal data in such a way that when errors occur they may becorrectable in the receive path. Modern error control codes aresophisticated that they can correct, e.g., up to 1 error in every 100bits with modest data overhead and latency. Optical distortioncompensation block 520 helps compensate for impairments in the opticaland electrical transmission paths. These could include compensation of,e.g., bandwidth limitations and inter-symbol interference. Themodulation conversion block 530 codes and decodes the multi-levelhigher-order modulation signals that are used at the transmitter andreceiver, and converts them to the simple two-level NRZ format used inthe lower speed interfaces.

FIGS. 6A and 6B are a simplified diagram of an electrical laser driverand TIA block diagram according to an embodiment of the presentinvention. This diagram is merely an example, which should not undulylimit the scope of the claims. One of ordinary skill in the art wouldrecognize many variations, alternatives, and modifications. As shown,the top part circuit (A) of an electrical laser driver and TIA blockshows a driver circuit for the modulator and the receiver circuit for aphoto diode detector (to be shown in FIG. 7 below). The electricaloutput of the top circuit (A) is used to drive the modulator. Themodulator imprints the electrical signal input on to the opticalcarrier. The output of the photo diode detector is the input to thebottom part circuit (B) of the electrical laser driver and TIA block.This circuit converts the current signal from the photo diode detectorinto a voltage signal which can then be processed by other circuits. Inan example, the electrical laser driver and TIA block is block 330included in the electrical silicon die block shown in FIG. 3.

FIG. 7 is a simplified diagram of a silicon photonic block diagramaccording to an embodiment of the present invention. This diagram ismerely an example, which should not unduly limit the scope of theclaims. One of ordinary skill in the art would recognize manyvariations, alternatives, and modifications. As shown, in an embodiment,a silicon photonic block 700 includes a laser source 710, a lasermodulator 720, a control loop 730, and one or more photo detectors 740.In a specific embodiment, the silicon photonic block 700 includes commonblocks of an optical sub-system including control loops. The transmitpath of the optical sub-system includes a laser source 710 which can beselected from a CW (continuous wave) DFB (distributed feedback) laseramong others. The laser source 710 provides the optical carrier. Theoutput from the laser source 710 is optically coupled into the lasermodulator 720.

The electrical data is converted to optical via the modulator formodulating the optical signal directly from the laser source 710. Themodulator 720 may be an electro-absorption modulator or a Mach-Zehnder(MZ) modulator, or others depending on embodiments. The output signalfrom the modulator 720 is then coupled to a fiber (not shown) forexternal transmission. The receive path of the optical sub-systemincludes the optical signal from the fiber coupled into one or morephoto diode detectors 740. The photo diode detector 740 converts theoptical data into electrical data. The control loops 730 are needed tocorrectly bias the laser source 710, the modulator 720, and the one ormore photo diode detectors 740. The bias control signals may includecurrent or voltage outputs used to setup the laser source, modulator,and the photo diode detector correctly. The control output signals mayalso be continually adjusted using the feedback from the devicesthemselves.

FIG. 8 is a simplified block diagram of a multi-chip module according toan alternative embodiment of the present invention. As shown, thepresent invention includes an integrated system on chip device. Thedevice is configured on a single silicon substrate member. The devicehas a data input/output interface provided on the substrate member andconfigured for a predefined data rate and protocol. The device has aninput/output block provided on the substrate member and coupled to thedata input/output interface. In an example, the input/output blockcomprises a SerDes block, a CDR block, a compensation block, and anequalizer block, among others. The device has a signal processing blockprovided on the substrate member and coupled to the input/output block.In an example, the signal processing block is configured to theinput/output block using a bi-direction bus in an intermediary protocol.The device has a driver module provided on the substrate member andcoupled to the signal processing block. In an example, the driver moduleis coupled to the signal processing blocking using a uni-directionalmulti-lane bus. In an example, the device has a driver interfaceprovided on the substrate member and coupled to the driver module andconfigured to be coupled to a silicon photonics device. In an example,the driver interface is configured to transmit output data in either anamplitude modulation format or a combination of phase/amplitudemodulation format or a phase modulation format. In an example, thedevice has a receiver module comprising a TIA block provided on thesubstrate member and to be coupled to the silicon photonics device usingpredefined modulation format, and configured to the signal processingblock to communicate information to the input/output block fortransmission through the data input/output interface. In an example, thedevice has a communication block provided on the substrate member andoperably coupled to the input/output block, the signal processing block,the driver block, and the receiver block, among others. The device has acommunication interface coupled to the communication block. The devicehas a control block provided on the substrate member and coupled to thecommunication block.

In an example, the signal processing block comprises a FEC block, asignal processing block, a framing block, a protocol block, and aredundancy block, among others. The driver module is selected from acurrent drive or a voltage driver in an example. In an example, thedriver module is a differential driver or the like. In an example, thesilicon photonics device is selected from an electro absorptionmodulator or electro optic modulator, or a Mach-Zehnder. In an example,the amplified modulation format is selected from NRZ format or PAMformat. In an example, the phase modulation format is selected from BPSKor nPSK. In an example, the phase/amplitude modulation is QAM. In anexample, the silicon photonic device is configured to convert the outputdata into an output transport data in a WDM signal. In an example, thecontrol block is configured to initiate a laser bias or a modulatorbias. In an example, the control block is configured for laser bias andpower control of the silicon photonics device. In an example, thecontrol block is configured with a thermal tuning or carrier tuningdevice each of which is configured on the silicon photonics device. Inan example, the SerDes block is configured to convert a first datastream of N into a second data stream of M.

FIG. 9 is a simplified block diagram of data flow according to anembodiment of the present invention. As show is a stream of incomingdata, which processed through multiple blocks. The blocks include, amongothers, forward error correction, and other encoding, Digital SignalProcessing (DSP) multi-level coding, pre-compression, and digital toanalog coding. The blocks also include non-DSP forward error correction,and a block corresponding to a laser diode or driver, among others. Inan example, in the absence of a FEC from a host process, techniquesinclude use of CDR2 type FEC, which is internal to the CMOS chip. In anexample, FEC can be striped across each or all of data lanes. Of course,there can be variations, modifications, and alternatives.

In an implementation of embodiment of the present invention, the digitalsignal processing is performed with a configurable multi-rate format forproducing data packet modulated with multi-channel-multi-bit-rate. Forexample, the electrical data can be modulated into a rate format with1×40 G bits per packet. The same data can also be modulated into 4packets with a rate of 10 G bits per packet. Alternatively, 100 G datacan be modulated into 1×100 G, 2×50 G, 4×25 G, or 10×10 G rate formatfor driving corresponding optical interface for transmitting a laser of1 wavelength in 100 G bit rate, multiplexed laser of 2 wavelengths in 50G bit rate, multiplexed laser of 4 wavelengths in 25 G bit rate, ormultiplexed laser of 10 wavelengths in 10 G bit rate. All the dataprocessing and pre-distribution are configurable by encoding into thedigital processing block that executes a wavelength divisional scheme todetermine the proper date rate for transmission depending onapplications of the data.

FIG. 10 is a simplified diagram illustrating a redundant laserconfiguration at a drive stage according to an embodiment of the presentinvention. In an example, the invention provides an integrated system onchip device having a redundant laser or lasers configured for eachchannel. In an example, the device has a plurality of laser devicesconfigured on the silicon photonics device. At least a pair of laserdevices is associated with a channel and coupled to a switch to selectone of the pair of laser devices to be coupled to an optical multiplexerto provide for a redundant laser device.

FIG. 11 is a simplified diagram illustrating a built-in self test usingan optical loop back according to an embodiment of the presentinvention. As shown are a TX multiplexer and an RX multiplexer for asilicon photonics device. In an example, the present invention providesan integrated system on chip device having a self test using a loop backtechnique. In an example, the device has a self-test block provided onthe substrate. In an example, the self test block is configured toreceive a loop back signal from at least one of the signal processingblock, the driver module, or the silicon photonics device. In anexample, the self test block comprises a variable output power switchconfigured to provide a stress receiver test from the loop back signal.Also shown is an isolation switch between RX and TX.

In an example, the present technique allows a loop back test capabilityon the device, which is now a silicon photonic application specificintegrated circuit or a communication system on chip device, asdescribed. In an example, the technique is provided for diagnostic andsetup during power up sequence. In an example, an optical tap coupler onthe output side connected to the input side as shown. In an example asshown, x (e.g., <10%) is selected to reduce and/or minimize an impact anoutput power as well an impact at the input power given that input poweris generally much lower than the output power. In an example, to preventcrosstalk in the present loop back path, an isolation switch has beenconfigured as shown. In an example, without the isolation switch thereis undesirably direct crosstalk between the output and input as shown.In an example, about 30 dB isolation is included to prevent coherentcrosstalk. Of course, there can be variations.

FIG. 12 is a simplified diagram illustrating a built-in self testconfigured for optical testing according to an embodiment of the presentinvention. In an example, the present invention provides an integratedsystem on chip device having a built-in self test technique. As shownare a TX multiplexer and an RX multiplexer for a silicon photonicsdevice. A broad band source is coupled to each of the multiplexers.Multiple sources can also be included. In an example, the device has aself test block configured on the silicon photonics device and to beoperable during a test operation. In an example, the self test blockcomprises a broad band source configured to emit electromagneticradiation from 1200 nm to 1400 nm or 1500 to 1600 nm to a multiplexerdevice. In an example, the broad band source can be an LED or othersuitable device. The device also includes a self test output configuredto a spectrum analyzer device external to the silicon photonics device.In an example, the technique can be provided during a calibrationprocess. That is, if after calibration, a center λ of each multiplexerchanged, the present technique including built-in light source willquantify or indicate the change in an example. In an example, thebroadband source in silicon photonics is a light source with no opticalfeedback, although there can be variations.

FIG. 13 is a simplified diagram illustrating a variable bias for opticalelements configured in a silicon photonic device according to anembodiment of the present invention. As shown are transfer curvesprovided for optical elements. In an example, the device has anintegrated system on chip device having a capability selectively adjusteach optical modulator to accommodate for fabrication tolerances,wavelength operation, and/or extinction ratio, among other parameters.The device has a single silicon substrate member and a data input/outputinterface provided on the substrate member and configured for apredefined data rate and protocol. In an example, the device has aninput/output block provided on the substrate member and coupled to thedata input/output interface. In an example, the input/output blockcomprises a SerDes block, a CDR block, a compensation block, and anequalizer block, among others. The device has a signal processing blockprovided on the substrate member and coupled to the input/output block.The signal processing block is configured to the input/output blockusing a bi-direction bus in an intermediary protocol. The device has adriver module provided on the substrate member and coupled to the signalprocessing block.

In an example, the driver module is coupled to the signal processingblocking using a uni-directional multi-lane bus. In an example, thedevice has a driver interface provided on the substrate member andcoupled to the driver module and configured to be coupled to a siliconphotonics device. In an example, the driver interface is configured totransmit output data in either an amplitude modulation format or acombination of phase/amplitude modulation format or a phase modulationformat. In an example, the device has a receiver module comprising a TIAblock provided on the substrate member and to be coupled to the siliconphotonics device using predefined modulation format, and configured tothe signal processing block to communicate information to theinput/output block for transmission through the data input/outputinterface. In an example, the device has a communication block providedon the substrate member and operably coupled to the input/output block,the signal processing block, the driver block, and the receiver block,and among others. The device has a communication interface coupled tothe communication block and a control block provided on the substratemember and coupled to the communication block.

In an example, the device has a variable bias block configured with thecontrol block. In an example, the variable bias block is configured toselectively tune each of a plurality of laser devices provided on thesilicon photonics device to adjust for at least a wavelength ofoperation, a fabrication tolerance, and an extinction ratio. As shown isa plurality of driver blocks. Each of the driver blocks is coupled to avoltage rail, and is configured with a variable voltage device toselectively tune each of the laser devices. In an example, each of thelaser devices can be configured with an optical modulator(s) such aselectro-absorption modulators, electro-optical modulators, among others,which often couple to a direct current power or bias. In an example, theDC bias is a function of wavelength of operation and also of fabricationtolerances, among other factors. In an example, the present biascircuitry accommodates and/or corrects for any bias variations, whiledesirably controlling power. Of course, there can be variations,modifications, and alternatives.

FIG. 14 is a simplified diagram illustrating wavelength tuningconfigured to silicon photonic device according to an embodiment of thepresent invention. In an example, the present tunable laser uses a setof rings with resonant frequencies that a slightly different. In anexample, the technique use a vernier effect to tune the laser over awide frequency range—limited by the bandwidth of the gain region. In anexample, the vernier desirably would be held in lock with respect to oneanother. In an example, the technique uses a dither frequency on one ofthe biases (e.g., heater) and lock the ring to the maximum transmissionof the second ring, although there can be variations. As shown, resonantcombs are generally misaligned in an example. When thermally tuned,techniques can be used to selectively align one of the combs to anothercomb or spatial reference. In an example, to maintain alignment, thetechnique dithers the signal to one of the rings. Of course, there canbe variations, alternatives, and modifications.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. Therefore, the above description and illustrations should not betaken as limiting the scope of the present invention which is defined bythe appended claims.

What is claimed is:
 1. A monolithically integrated system-on-chip deviceconfigured for a multi-rate and selected format of data communication,the device comprising: a single silicon substrate member; a datainput/output interface provided on the substrate member and configuredfor a predefined data rate and protocol; an input/output block providedon the substrate member and coupled of the data input/output interface,the input/output block comprising a SerDes block, a CDR block, acompensation block, and an equalizer block, the SerDes block beingconfigured to convert a first data stream of N into a second data streamof M, each of the first data stream having a first predefined data rateat a first clock rate and each of the second data stream having a secondpredefined data rate at a second clock rate; a signal processing blockprovided on the substrate member and coupled to the input/output block,the signal processing block configured to the input/output block using abi-direction bus in an intermediary protocol; a driver module providedon the substrate member and coupled to the signal processing block, thedriver module coupled to the signal processing blocking using auni-directional multi-lane bus; a driver interface provided on thesubstrate member and coupled to the driver module and configured to becoupled to a silicon photonics device, the driver interface beingconfigured to transmit output data in either an amplitude modulationformat or a combination of phase/amplitude modulation format or a phasemodulation format; a receiver module comprising a TIA block provided onthe substrate member and to be coupled to the silicon photonics deviceusing predefined modulation format, and configured to the signalprocessing block to communicate information to the input/output blockfor transmission through the data input/output interface; a lasercoupled to the silicon photonics device; a communication block providedon the substrate member and operably coupled to the input/output block,the signal processing block, the driver block, and the receiver block; acommunication interface coupled to the communication block; and acontrol block provided on the substrate member and coupled to thecommunication block.
 2. The device of claim 1 wherein the signalprocessing block comprises a FEC block, a digital signal processingblock, a framing block, a protocol block, and a redundancy block.
 3. Thedevice of claim 1 wherein the driver module is selected from a currentdrive or a voltage driver.
 4. The device of claim 1 wherein the drivermodule is a differential driver.
 5. The device of claim 1 wherein theamplified modulation format is selected from NRZ format or PAM format.6. The device of claim 1 wherein the phase modulation format is selectedfrom BPSK or nPSK.
 7. The device of claim 1 wherein the signalprocessing block comprises a multi-rate format in data packet modulatedwith multi-channel-multi-bit-rate of 1×40 G, 4×10 G, 1×100 G, 2×50 G,4×25 G, or 10×10 G for driving corresponding optical interface fortransmitting a laser of 1 wavelength in 40 G, or 4 wavelengths in 10 G,or 1 wavelength in 100 G, 2 wavelengths in 50 G, 4 wavelengths in 25 G,or 10 wavelengths in 10 G.
 8. The device of claim 1 wherein thephase/amplitude modulation is QAM.
 9. The device of claim 1 wherein thesilicon photonic device is configured to convert the output data into anoutput transport data in a WDM signal.
 10. The device of claim 1 whereinthe control block is configured to initiate a laser bias or a modulatorbias.
 11. The device of claim 1 wherein the control block is configuredfor laser bias and power control of the silicon photonics device. 12.The device of claim 1 wherein the control block is configured with athermal tuning device or carrier tuning device each of which isconfigured on the silicon photonics device; wherein the SerDes block isconfigured to convert a first data stream.
 13. A method of using amonolithically integrated system-on-chip device configured for amulti-rate and selected format of data communication, method comprising:using the device comprising: a single silicon substrate member; a datainput/output interface provided on the substrate member and configuredfor a predefined data rate and protocol; an input/output block providedon the substrate member and coupled of the data input/output interface,the input/output block comprising a SerDes block, a CDR block, acompensation block, and an equalizer block, the SerDes block beingconfigured to convert a first data stream of N into a second data streamof M, each of the first data stream having a first predefined data rateat a first clock rate and each of the second data stream having a secondpredefined data rate at a second clock rate; a signal processing blockprovided on the substrate member and coupled to the input/output block,the signal processing block configured to the input/output block using abi-direction bus in an intermediary protocol; a driver module providedon the substrate member and coupled to the signal processing block, thedriver module coupled to the signal processing blocking using auni-directional multi-lane bus; a driver interface provided on thesubstrate member and coupled to the driver module and configured to becoupled to a silicon photonics device, the driver interface beingconfigured to transmit output data in either an amplitude modulationformat or a combination of phase/amplitude modulation format or a phasemodulation format; a receiver module comprising a TIA block provided onthe substrate member and to be coupled to the silicon photonics deviceusing predefined modulation format, and configured to the signalprocessing block to communicate information to the input/output blockfor transmission through the data input/output interface; a lasercoupled to the silicon photonics device; a communication block providedon the substrate member and operably coupled to the input/output block,the signal processing block, the driver block, and the receiver block; acommunication interface coupled to the communication block; and acontrol block provided on the substrate member and coupled to thecommunication block; initiating a signal from the control block toinitiate a laser bias or a modulator bias; and tuning, using the controlblock, the silicon photonics device.
 14. The method of claim 13 whereinthe signal processing block comprises a FEC block, a digital signalprocessing block, a framing block, a protocol block, and a redundancyblock.
 15. The method of claim 13 wherein the driver module is selectedfrom a current drive or a voltage driver.
 16. The method of claim 13wherein the driver module is a differential driver.
 17. The method ofclaim 13 wherein the amplified modulation format is selected from NRZformat or PAM format.
 18. The method of claim 13 wherein the phasemodulation format is selected from BPSK or nPSK.
 19. The method of claim13 wherein the signal processing block comprises a multi-rate format indata packet modulated with multi-channel-multi-bit rate of 1×40 G, 4×10G, 1×100 G, 2×50 G, 4×25 G, or 10×10 G for driving corresponding opticalinterface for transmitting a laser of 1 wavelength in 40 G, or 4wavelengths in 10 G, or 1 wavelength in 100 G, 2 wavelengths in 50 G, 4wavelengths in 25 G, or 10 wavelengths in 10 G.
 20. The method of claim13 wherein the phase/amplitude modulation is QAM; wherein the siliconphotonic device is configured to convert the output data into an outputtransport data in a WDM signal; wherein the SerDes block is configuredto convert a first data stream of N into a second data stream of M of Ninto a second data stream of M.